The present invention relates to a process for producing modified gelatinized cereal flours, particularly to a process for producing a gelatinized cereal flour having a porous structure by adding an alcohol to a gelatinized cereal flour and freeze-drying the mixture. The present invention also relates to the porous gelatinized cereal flour thus produced. Further, the present invention relates to a fragrance adsorbent and an emulsion stabilizer that are composed of a gelatinized cereal flour.
On account of their unique polymer characteristics, native and processed starches are used in a broad range of applications including food use. In particular, gelatinized starches or processed starches that are manufactured by suspending native starches in water and then drying by heating them have long been used in various applications since they have good utility and storage stability and because they can be produced by simple techniques using drum dryers and other readily available devices. However, the recent changes in people's life style, particularly in the foods they eat, have caused corresponding changes in the form of various foodstuffs or raised a need for the development of new functional materials in various fields, and it has become increasingly difficult to obtain a desired product merely by utilizing the properties of native starches and conventional processed starches including gelatinized starches.
Gelatinized starches have markedly different properties depending upon the process of their production or the starting materials from which they are produced. Thus, gelatinized starches that are adapted for various uses can be manufactured by selecting proper production process, conditions and starting materials. With a view to acquiring new properties by making use of this advantageous nature of gelatinized starches, various methods for their production have been developed. It has, for example, been reported that when raw starch is converted to a gelatinized form in an aqueous alcohol solution under pressure, gelatinized starch that almost completely retains the shape of granules in the raw starch and which resists agglomeration when dissolved in water can be obtained (Japanese Patent Public Disclosure No. 63-49054). A problem with the conventional gelatinized starch is that when it is dissolved in water, agglomerates are often formed, thus making it unsuitable for use as a constituent material of bean-jam cakes. In order to solve this problem, it has been proposed that a gelatinized cereal flour such as kanbai-ko (gelatinized glutinous rice flour) be mixed with water and an alcohol and dried with heat (Japanese Patent Public Disclosure No. 63-49050). Since water penetration into the treated cereal flour is suppressed, it will not experience rapid swelling upon water absorption, thereby resisting agglomeration. The use of an oxidized starch as an emulsion stabilizer after enzyme treatment has also been reported (Japanese Patent Publication No. 58-1622).
A method of suspending starch in water, heating the suspension and freeze-drying it in vaccum has drawn increasing attention as a technique for producing processed starches having new properties. The starch thus produced has been reported to have a greater ability to absorb oils and other fluids than the raw starch. However, various process conditions have to be considered before drying methods such as freeze-drying can be effectively utilized.
Even if freeze-drying is directly applied as a drying method instead of thermal drying for a mixture of gelatinized cereal flour with water and an alcohol, a fine structure cannot be effectively created in the surface of starch granules and a desired porous structure is not attainable.